perpendicular slope & equation of perpendicular lines

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LESSON 5-8 Perpendicular Slope & Equation of Perpendicular Lines

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Perpendicular Slope & Equation of Perpendicular Lines. Lesson 5-8. Math Vocabulary. Perpendicular Lines: two lines on a graph, that DO intersect, forming a right angle, based on opposite slope. Finding Parallel Slope…. Perpendicular Lines have… The opposite/reciprocal slope! - PowerPoint PPT Presentation

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Page 1: Perpendicular Slope & Equation of Perpendicular Lines

LESSON 5-8

Perpendicular Slope & Equation of Perpendicular

Lines

Page 2: Perpendicular Slope & Equation of Perpendicular Lines

Math Vocabulary

Perpendicular Lines:two lines on a graph, that DO intersect,

forming a right angle, based on opposite slope

Page 3: Perpendicular Slope & Equation of Perpendicular Lines

Finding Parallel Slope…

Perpendicular Lines have…The opposite/reciprocal

slope!

If y = 3/5 x – 4

m = 3/5

then perpendicular slope perpendicular m = - 5/3

Page 4: Perpendicular Slope & Equation of Perpendicular Lines

Finding Parallel Slope…

Find the slope of a line perpendicular to the equation…

y = -5 x – 3

m = -5

perpendicular m = 1/5

Find the slope of a line perpendicular to the equation…

x – 3y = 7

*Needs to be in y = mx + b

x – 3y = 7 -x -x -3y = -x + 7 -3 -3 -3

y = 1/3 x – 7/3

m = 1/3

perpendicular m = - 3

Page 5: Perpendicular Slope & Equation of Perpendicular Lines

Finding Perpendicular Slope…

Find the slope of a line perpendicular to the equation…

y = -4x + 7

m = -4

perpendicular m = ¼

Find the slope of a line perpendicular to the equation…

3y + 6x = 12

*Needs to be in y = mx + b

m = -2

perpendicular m = ½

Page 6: Perpendicular Slope & Equation of Perpendicular Lines

Equation of a line with Perpendicular Slope…

Finding the equation of a line perpendicular to y = -4x + 1

AND… that passes thru the point (-8, 0)

1) Name the current slope m = -4

2) Name the perpendicular slopeperpendicular m = 1/4

2) Solve to write the equation with…

m = 1/4, thru (-8, 0)

y = mx + b0 = ¼ (-8) + b0 = -8/4 + b0 = -2 + b+2 +2 2 = b

Eq. y = ¼ x + 2

Page 7: Perpendicular Slope & Equation of Perpendicular Lines

Practice…

Find the parallel & perpendicular slope of each equation of a line…

a) y = - 8/3x + 5 parallel m =perp m =

b) 15x + 3y = -3 parallel m =perp m =

c) Write the equation of a line perpendicular to y = -2x + 1, and that passes thru (-4, 3)

Page 8: Perpendicular Slope & Equation of Perpendicular Lines

Homework

p. 253-254 #13-17, 21-23, 42, 43